ISIL takes a different approach to it its main strategy when under pressure

Washington Post:

The Islamic State’s newest goal: Unleash chaos, carnage in Baghdad

U.S. and Iraqi military officials say the militants are attempting to stall any offensive to retake their strongholds in Fallujah and Mosul by distracting forces in the capital.

In the past, ISIL would launch offenses in a different direction from the avenue of attack of adversaries.  They would use traditional combat persisting warfare attacking using pickup trucks for mobility.   The increased US air support for government and Kurdish forces has made that tactic no longer viable.  Now they are trying to relieve pressure by using human bomb attacks in Iraqi cities.